Project 3 Roadmap

1
Project 3 Roadmap

• Multilevel Feedback Scheduling
• Semaphores
• Passing Parameters to New Processes

2
Multilevel Feedback Scheduling

• Get_Time() - trivial
• Multilevel Feedback Scheduling
• add current queue/blocked state for each Thread
• create 4 queues a thread is intially in q0
  (except IDLE thread)
• end of quanta ?
• if blocked promote
• if has run demote
• make sure your Set_Scheduling_Policy() works
  before stuff gets complicated
• becomes blocked in Wait()

3
Semaphores

• drilling, drilling
• rough guideline
• add two files sem.h/sem.c
• create a semaphore structure
• each has a thread queue, count, name, etc
• P/V semantics
• P decrease, block if needed
• V increase, never blocks

4
Passing Parameters to New Processes(I)

• start with processing in shell
• pass the string via Spawn_Program syscall
• (drop the of course)
• kernel takes exec name, creates UserThread
• whole command line gets into user memory space
• time for Entry() to do lots of stuff
• recover cmd line
• split into argv
• call Main(argc, argv)

User
Kernel
User
5
Passing Parameters to New Processes(II)
6
Passing Parameters to New Processes(III)